The collection of articles in this volume represents the proceedings of the inau- gural Conference of the Institute of Theoretical Matter Physics at the University of Florence, Italy, June 7-13, 1990. The aim of this Institute (sponsored by the Con- sorzio Interuniversitario di Fisica della Materia, INFM) is to foster interdisciplinary approaches to theoretical problems in Solid State, Electronics and Optics. Corre- spondingly, the Conference surveyed a broad scope of modern analytic techniques in nonlinear science and their application to novel liquids, solids and optical environ- ments. The Conference was held at Centro Studi CISL, a magnificent Villa up to Florence. The major topics addressed through survey and specialized lectures, discussions and posters were: Complexity and Coherence in spin glasses, associative distribu- tive memory, low dimensional electronic materials, magnets, Josephson junction ar- rays, optics, semiconductors, convection cells, material science, high-temperature superconductivity; Physics of Quantum Devices such as nonlinear feedback oscilla- tors, macroscopic quantum tunneling, hetero structures, quantum ballistic devices, tunneling in atomic devices; Field Theory and Statistical Mechanics, especially for soliton-bearing and quantum chaotic systems. Many exciting ideas and results were presented and debated in lively fashion. Perhaps two major themes were evident throughout the workshop.

An international workshop on Elementary Excitations and Fluctuations in Magnetic Systems was held in San Miniato, Italy, for five days beginning 28 May, 1984. The workshop comprised eight working sessions that contai- ned a total of 43 invited talks, and 58 scientists were in attendance from 14 countries. Our aim was to review some topics of current interest in the statistical physics of magnetic materials and models, with an emphasis on theoretical studies and confrontations between these and experimental and computer simulation data. book contains summary papers written by the invited speakers, and This the material will be of immediate interest to graduate students and resear- chers engaged in studies of magnetic properties. There is, perhaps, no ef- fective way to record and convey the benefit of the numerous discussions between the participants that are a significant integral feature of a work- shop. The magnificent .venue of the workshop, I Cappuccini, was made availa- ble to us by the.Cassa di Risparmio San Miniato. Financial support for the workshop was received from Consiglio Nazionale delle Ricerche, Universita degli Studi di Firenze and the Gruppo Nazionale Struttura,della Materia. Our administrative load and the burden of preparing the proceedings for publication was made light by the talents of Carla Pardini (CNR, Florence), and Caroline Monypenny and Jane Warren (Rutherford Appleton Laboratory). Fina 11y, we wish to thank all the participants for their attendance and individual contributions to the success of the workshop.